This invention relates to an integrated ratio pump and check valve apparatus for pumping a plurality of discrete liquid volumes to points of use of the liquid volumes. More particularly, this invention relates to an integrated ratio displacement pump and check valve apparatus for pumping a plurality of discrete liquid volumes to points of use.
At the present time, discrete liquid volumes are pumped with a syringe pump comprising a barrel, a face seal which moves within the barrel and a reciprocating plunger attached to the face seal. The syringe pump includes a valve construction formed of a polymeric composition which directs the pumped liquid volumes to a point of use. The valve construction includes a housing (stator) having a hollow, essentially interior surface into which is press fit a mating rotor. The rotor is provided with fluid passageways that control flow of liquid into the syringe pump and flow of liquid from the syringe pump while providing sealing between a pump inlet and a pump outlet. This configuration of syringe pump and rotor-stator valve requires two motors, one to drive the syringe and a second to drive the rotor.
While the available syringe pumps have been useful for their intended purpose, they also have disadvantages. In order to attain a tight fit between the barrel and the face seal, the manufacturing of both the barrel and face seal must be made at tight tolerances. In addition, when utilizing the most commonly used materials comprising a glass barrel and a polytetrafluoroethylene (PTFE) face seal, undesirable shedding of the PTFE occurs which contaminates the liquid being pumped. Furthermore, a tight fit between the barrel and face seal results in chattering of the face seal during its movement within the barrel. This leads to a loss of control of the liquid volume being pumped. In addition, the average useful life of presently available syringe pumps is only about 10 to about 100,000 cycles.
The presently available syringe pumps also are capable of pumping only a single liquid. Oftentimes it is desirable to provide a mixture of two or more liquid compositions for specific purposes. The provision of such liquid mixtures is not possible with presently available syringe pumps.
Accordingly, it would be desirable to provide a pump apparatus capable of delivering discrete liquid volumes to a point of use such as different areas of a sample tray in a manner which is repeatable for long time periods of 1,000,000 cycles or more. In addition, it would be desirable to provide such a pump apparatus which avoids shedding of particles during pumping. Furthermore, it would be desirable to provide such a pump which eliminates the need for a motor to activate a seal in order to direct fluid to a desired point of use. In addition, it would be desirable to provide such a pump apparatus capable of pumping a plurality of liquids in precise volume ratios.